The next two songs following the introduction in the long melody are both original Lennon/McCartney compositions and are both written mainly by John: "Sun King/Mean Mister Mustard". A demo version of "Mean Mister Mustard" can be heard as the fourth track of the Apple/ EMI 3-LP/2-CD "Anthology 3" which was performed in May 1968 as part of the "Esher Demos".
During the recording of "Sun King/Mean Mister Mustard"; the working title at EMI was "Part Two: Here Comes The Sun King". It was probably shortened due to the similarity of the previous George Harrison composition "Here Comes The Sun".
The basic track for "Sun King/Mean Mister Mustard" was completed in 35 takes on July 24 1969 at EMI studio two. The instrumentation was John on guide vocal and acoustic guitar, George Harrison on electric guitar, Paul on bass and Ringo on drums. At one point during this session, The Beatles started busking "Ain't She Sweet" (Gene Vincent version) and the jam was caught on tape and is available in stereo on the Apple/EMI 3-LP/2-CD "Anthology 3".
The next day on July 25 1969 and once again at EMI studio two, overdubs included vocals, piano and organ.
Finally, four days later on July 29 1969 at EMI studio three, more vocal overdubs and bongos, tambourine and maracas were added to the track.
The next day on Wednesday July 30 1969 from the control room of EMI studio two, "Sun King/Mean Mister Mustard" was given a rough stereo mix and placed within the huge melody to see if it would work. The cross fade between "You Never Give Me Your Money" and "Sun King" posed a bit of a problem but that was worked out with sound effects added the following month (see previous post).
On Tuesday August 14 1969 from the control room of EMI studio two, "Sun King/Mean Mister Mustard" were given four attempts at a stereo mix with the fourth attempt being used on the commercial version.
On Thursday August 21 1969 in room 4 of EMI studios, the final crossfading between "You Never Give Me Your Money" and "Sun King" was completed in stereo using the sound effects.
"Sun King/Mean Mister Mustard" are available on the Apple LP/CD "Abbey Road". A silly version of "Sun King" entitled "Gnik Nus" which is basically the vocal track played backwards is available as track 08 on the Apple/EMI 2-LP/CD "Love".